Cooling system for small watercraft

ABSTRACT

A cooling system particularly suited for use in a small watercraft. The cooling system desirably supplies coolant to, and evacuates coolant from an engine of the watercraft. The engine includes an engine body defining at least one water jacket therein. A pressure actuated valve is desirably positioned upstream from the water jacket. A temperature actuated valve is desirably positioned downstream from the water jacket. The pressure actuated valve opens at a predetermined threshold fluid pressure to allow coolant to bypass, desirably, both the water jacket of the engine and the temperature actuated valve. Preferably, the threshold fluid pressure is lower than a fluid pressure that will damage the temperature actuated valve.

PRIORITY INFORMATION

[0001] This application is based on, and claims priority to, Japanese Patent Application No. 2001-019988, filed Jan. 29, 2001, the entire contents of which are expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is related to engine cooling systems in general. More particularly, the present invention is related to an engine cooling system particularly suited for incorporation in a small watercraft.

[0004] 2. Description of the Related Art

[0005] Personal watercraft, like other applications that use internal combustion engines for propulsion, are experiencing considerable public and governmental pressure to improve not only their performance, but also their exhaust emissions level. For example, due at least in part to the emissions generated by two-stroke powered watercraft, certain recreational areas have banned the operation of such watercraft. These bans have decreased the popularity of personal watercraft, and have caused manufacturers of these types of watercraft to consider replacing conventional two-stroke type internal combustion engines with four-stroke engines to power the watercraft and/or other means to reduce emissions levels.

[0006] Although typical four-stroke type engines inherently produce less exhaust emissions than similar two-stroke engines, it nonetheless remains important to maintain the operating temperature of the four-stroke engine within a relatively narrow temperature range in order to fully realize the reduced emissions levels. For this purpose, a temperature actuated valve, or thermostat, is typically employed within the cooling system of the watercraft to maintain the desired operating temperature of the engine.

[0007] However, because the cooling water is typically supplied by the jet pump unit of the watercraft, the fluid pressure of the cooling water supplied to the cooling system tends to greatly fluctuate. The fluid pressure may reach a magnitude such that cooling water is undesirably forced past the thermostat even though the cooling water temperature is not above the normal opening temperature of the thermostat. This may happen for a variety of reasons, including the inherent design of the thermostat not being capable of retaining fluid above a certain pressure. Similarly, normal manufacturing tolerances may prevent a typical thermostat from retaining fluid above a certain pressure, even if the thermostat is in a closed position, or closed orientation. Such a pressure that undesirably forces fluid past the thermostat may be referred to as a “blowby” pressure. Typically, the blowby pressure is an inherent property of the temperature sensitive valve.

SUMMARY OF THE INVENTION

[0008] One aspect of the present invention is the realization that blowby cooling water flow past the thermostat, when the thermostat is in a closed orientation, is likely to result in permanent damage and malfunctioning of the thermostat. If the thermostat becomes damaged and, as a result, is unable to accurately maintain the desired operating temperature of the engine, the exhaust emission performance of the engine suffers. Accordingly, one aspect of the present cooling system is to provide a pressure sensitive valve in the engine cooling system. Preferably, the pressure sensitive valve is upstream from the thermostat and the engine and is configured to open at a fluid pressure lower than a blowby fluid pressure of the thermostat. Such a configuration inhibits the cooling water pressure from reaching a magnitude that may cause damage to the thermostat and prevents cooling water from cooling the engine when the valve is open.

[0009] One aspect of the present invention involves a small watercraft comprising a hull defining an engine compartment. An internal combustion engine is disposed in the engine compartment and a propulsion device is driven by the engine. The engine has an engine body defining a combustion chamber and a cooling jacket at least partially surrounding the combustion chamber. A cooling system is in fluid communication with the cooling jacket and supplies cooling fluid to the cooling jacket. The cooling system additionally includes a pressure actuated valve and a temperature actuated valve, the cooling jacket being between the pressure actuated valve and the temperature actuated valve.

[0010] Another aspect of the present invention involves a method of cooling a watercraft engine having an engine body. The method comprises providing a cooling system to deliver a supply of cooling fluid to a water jacket of the engine body. Detecting a temperature of the cooling fluid downstream from the water jacket with a thermostat and substantially preventing cooling water from evacuating the water jacket if the temperature is below a predetermined threshold. The method further includes detecting a pressure of the cooling fluid upstream from the water jacket and allowing at least a portion of the cooling fluid to bypass the thermostat if the pressure is above a predetermined threshold. The predetermined threshold being a pressure lower than a blow-by pressure of the temperature actuated valve.

[0011] A further aspect of the present invention involves a marine engine comprising an engine body defining at least one combustion chamber and a cooling jacket at least partially surrounding the at least one combustion chamber. A cooling system in fluid communication with the cooling jacket, the cooling system supplying cooling fluid to the cooling jacket. The cooling system further comprising a pressure actuated valve and a temperature actuated valve. The pressure actuated valve being upstream from the temperature actuated valve and configured to permit the cooling fluid to bypass the temperature actuated valve if a pressure of the cooling fluid is above a predetermined threshold. The predetermined threshold being a pressure lower than a blow-by pressure of the temperature actuated valve.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above-mentioned and other features of the present invention are described below with reference to drawings of a preferred embodiment of an engine cooling system for a watercraft. The illustrated embodiment of the cooling system is intended merely to illustrate, but not to limit, the invention. The drawings contain fourteen figures.

[0013]FIG. 1 is a side elevational view of a personal watercraft having a cooling system constructed in accordance with a preferred embodiment of the present invention, with certain internal components (e.g., an engine) illustrated in phantom;

[0014]FIG. 2 is a top plan view of the watercraft of FIG. 1;

[0015]FIG. 3 is a front, top and starboard side perspective view of the engine shown in FIG. 1 with an air box positioned atop of the engine;

[0016]FIG. 4 is a top plan view of the engine illustrating showing an exhaust manifold and with the air box removed;

[0017]FIG. 5 is a port side elevational view of the exhaust manifold shown in FIG. 4;

[0018]FIG. 6 is a bottom plan view of the exhaust manifold shown in FIG. 5. A pair of conduit portions thereof are shown in phantom;

[0019]FIG. 7 is a starboard side elevational view of the engine and a portion of the exhaust system with several internal passages of the exhaust system shown in phantom;

[0020]FIG. 8 is a partial sectional and front elevational view of the engine and exhaust system shown in FIG. 7;

[0021]FIG. 9 is a cross sectional view of a portion of the exhaust system including an exhaust pipe and water-lock;

[0022]FIG. 10 is a schematic representation of the cooling system included in the engine shown in FIG. 3 particularly showing coolant passage connections between various components of the engine;

[0023]FIG. 11 is a rear elevational view of the engine illustrating a valve train drive arrangement and the position of a pressure actuated valve of the cooling system shown in FIG. 10;

[0024]FIG. 12 is an enlarged starboard side elevational view of the engine shwon in FIG. 4 and showing the pressure actuated valve;

[0025]FIG. 13 is a cross section view of the pressure actuated valve and a portion of the engine shown in FIG. 12; and

[0026]FIG. 14 is a cross section view of a temperature actuated valve of the cooling system shown in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] With reference to FIGS. 1-14, an improved engine cooling system for a watercraft 20 is described below. The cooling system allows the engine, and various components thereof, to be more precisely cooled so as to substantially prevent incomplete combustion, and prevent damage to components of the cooling system.

[0028] Although the present engine cooling system is illustrated in connection with a personal watercraft, the illustrated engine can be used with other types of watercrafts as well, such as, for example, but without limitation, small jet boats and the like. Alternative embodiments of the present invention will become readily apparent to those of skill in the art from the following detailed description of the preferred embodiment having reference to the attached figures, the invention not being limited to the preferred embodiment disclosed.

[0029] Before describing the cooling system of the watercraft 20, an exemplary personal watercraft 20 will first be described in general detail to assist the reader's understanding of the enviromnent of use. The watercraft 20 will be described in reference to a coordinate system wherein a longitudinal axis extends from bow to stern and a lateral axis from port side to starboard side normal to the longitudinal axis. In addition, relative heights are expressed as elevations in reference to the undersurface of the watercraft 20. In various figures, an arrow F_(R) is used to note the direction in which the watercraft travels during normal forward operation.

[0030] The watercraft 20 has a hull, indicated generally by the reference numeral 22. The hull 22 can be made of any suitable material, however, a presently preferred construction utilizes molded fiberglass reinforced resin. The hull 22 generally has a lower hull section 24 and an upper deck section 26, as shown in FIG. 1. A bond flange 28 can connect the lower hull section 24 to the upper deck section 26. Of course, any other suitable means may be used to interconnect the lower hull section 24 and the upper deck section 26. Alternatively, the lower hull section 24 and the upper deck section 26 may be integrally formed.

[0031] As viewed in the direction from the bow to the stern of the watercraft 20, the upper deck section 26 includes a bow portion 30 and a rider's area 32. Between the bow portion 30 and the rider's area 32, a control mast 34 is provided which supports a handlebar assembly 36. The handlebar assembly 36 controls the steering of the watercraft 20 in a conventional manner. The handlebar assembly 36 may also carry a variety of controls of the watercraft 20, such as, for example, a throttle control, a start switch and a lanyard switch (not shown).

[0032] The rider's area 32 lies behind the control mast 34 and includes a seat assembly 38. The seat assembly 38, at least in part, is formed by at least one seat cushion and, preferably, by a forward seat cushion 40 and a rearward seat cushion 42. The seat assembly 38 is supported by a raised pedestal 44. The raised pedestal 44 forms a portion of the upper deck 26, and has an elongated shape that extends longitudinally along the center of the watercraft 20. The seat cushions 40, 42 desirably are removably attached to a top surface of the raised pedestal 44 by one or more latching mechanisms (not shown) and cover the entire upper end of the pedestal 44 for rider and passenger comfort.

[0033] With reference to FIG. 2, an engine access opening 46 is located in the upper surface of the pedestal 44. The access opening 46 opens into an engine compartment 48 formed within the hull 22. One or both of the seat cushions 40, 42 normally cover and seal the access opening 46. When the seat cushion, or cushions 40, 42 are removed, the engine compartment 48 is accessible through the access opening 46.

[0034] The upper deck portion 26 of the hull 22 advantageously includes a pair of generally planar areas positioned on opposite sides of the seat pedestal 44, which define foot areas 50. The foot areas 50 extend generally along and parallel to the sides of the pedestal 44. In this position, the operator and any passengers sitting on the seat assembly 38 can place their feet on the foot areas 50 during normal operation of the watercraft 20. A non-slip (e.g., rubber) mat desirably covers the foot areas 50 to provide increased grip and traction for the operators and passengers.

[0035] With reference to both FIGS. 1 and 2, an engine 52 is mounted within the engine compartment 48 in any suitable manner. Preferably, the engine 52 is mounted to a liner (not shown) of the lower hull portion 24 with an assembly of resilient engine mounts 54, as is known in the art. Advantageously, the resilient engine mounts 54 attenuate engine vibrations transmitted to the hull 22 of the watercraft 20.

[0036] A fuel tank 56 is preferably arranged forwardly from the engine 52. A fuel filler conduit (not shown) preferably extends between the fuel tank 56 and the upper deck portion 26, and terminates in a fuel filler cap (not shown). Thus, access to the fuel tank 56 can be gained by removing the filler cap.

[0037] The watercraft 20 includes at least one ventilation duct. In the illustrated embodiment, a forward ventilation duct 58 and a rearward ventilation duct 60 are provided. The ventilation ducts 58, 60 are configured to guide air into and out of the engine compartment 48. Except for the ventilation ducts 58, 60, or any other ventilation devices (not shown) the engine compartment 48 is desirably substantially sealed so as to enclose the engine 52 of the watercraft 20 from the body of water in which the watercraft 20 is operated.

[0038] The lower hull section 24 is designed such that the watercraft 20 planes or rides on a minimum surface area at the aft end of the lower hull 24 in order to optimize the speed and handling of the watercraft 20 when up on plane. For this purpose, the lower hull section 24 generally has a V-shaped configuration formed by a pair of inclined sections that extend outwardly from a keel of the hull to the hull's sidewalls at a dead-rise angle. The inclined sections also extend longitudinally from the bow toward the transom of the lower hull 24. The sidewalls are generally flat and straight near the stem of the hull 24 and smoothly blend toward the longitudinal center of the watercraft 20 at the bow 30. The lines of intersection between the inclined sections and the corresponding sidewalls form the outer chines of the lower hull section 24.

[0039] Toward the transom of the watercraft 20, the inclined sections of the lower hull 24 extend outwardly from a recessed channel, or tunnel 62, that extends upwardly toward the upper deck 26. The tunnel 62 generally has a parallelepiped shape and opens through the transom of the watercraft 20.

[0040] A jet pump unit 61 (shown schematically in FIG. 10) is mounted within the tunnel 62 and includes an inlet formed in the lower surface of the lower hull section 24 which opens into a gullet of an intake duct leading the jet pump unit 61. The intake duct leads to an impeller housing 63 (FIG. 10) in which an impeller 170 (FIG. 10) of the jet pump 61 operates. The impeller housing 63 also acts as a pressurization chamber and delivers a pressurized flow of water from the impeller housing 63 to a discharge nozzle 64 (FIG. 10). A steering nozzle (not shown) is supported at a downstream end of the discharge nozzle by a pair of vertically extending pivot pins. In an exemplary embodiment, the steering nozzle has an integral lever on one side that is coupled to the handlebar assembly 36 through, for example, a bowden-wire actuator, as known in the art. In this manner, an operator of the watercraft 20 can move the steering nozzle to effect directional changes of the watercraft 20.

[0041] Desirably, a ride plate (not shown) covers a portion of the tunnel 62 behind the inlet opening to close the jet pump unit 61 within the tunnel 62. In this manner, the lower opening of the tunnel 62 is closed to provide a planing surface for the watercraft 20.

[0042] Desirably, the engine 52 is an internal combustion engine and powers the jet pump unit 61 of the watercraft 20. In the illustrated embodiment, the engine 52 includes four in-line cylinders and operates on a four-cycle (i.e., four-stroke) principle. The engine 52 is positioned such that the row of cylinders is generally parallel to the longitudinal axis of the watercraft 20, running from bow to stern. The axis of each cylinder is desirably inclined relative to a vertical central plane of the watercraft 20, in which the longitudinal axis of the watercraft 20 lies. This engine type, however, is merely exemplary. Those skilled in the art will readily appreciate that the present cooling system can be used with a variety of engine types having other numbers of cylinders, having other cylinder arrangements (e.g., vertical V-type, W-type), and operating on other combustion principles (e.g., two-stroke diesel, and rotary principles).

[0043] A fuel supply system delivers fuel from the fuel tank 56 to the engine 52 in a manner known in the art. Although not illustrated, at least one pump desirably delivers fuel from the fuel tank 56 to the engine 52 through one or more fuel lines (not shown). The fuel lines extend to charge formers, which are configured to deliver charges of fuel to the combustion chambers of the engine 52 through inlet passages 66 (FIG. 4). The charge formers may be of any suitable arrangement, including carburetors, induction passage fuel injectors, or direct-inject fuel injectors.

[0044] With reference to FIGS. 1, 3 and 4, the engine 52 typically draws air from the engine compartment 48 through an engine air intake system. In the illustrated embodiment, the engine air intake system comprises an air intake chamber 68 positioned over the engine 52. The intake air chamber 68 includes an inlet 70 defined in a lower wall of the chamber 68. The inlet 70 extends upwardly into an interior of the chamber 68. An air filter element surrounds the interior end of the inlet 70 and is desirably sealed against the upper and lower inner surfaces of the chamber 68 such that air entering the chamber 68 through the inlet 70 must pass through the air filter element. Preferably, the air filter element includes both a water-resistant element and an oil resistant element, with the water-resistant element being positioned upstream from the oil resistant element along the direction of normal airflow.

[0045] The intake air chamber 68 also includes apertures for communicating with the intake passages 66. The charge formers are arranged to meter an amount of air entering the intake passages 66 and, thus, the combustion chamber of the engine, from the air intake chamber 68. In a preferred embodiment, the charger formers are positioned within the air intake chamber 68 so as to be protected from damage.

[0046] With reference to FIGS. 7 and 11, the engine 52 is formed of an engine body 72 having a cylinder block 74, a cylinder head 76 and a crankcase 78. As is conventional, one piston is supported for reciprocation within each cylinder bore 65 (one shown in FIG. 13) of the engine 52. Each piston is connected to a crankshaft 79 (FIG. 11) of the engine 52 by a connecting rod (not shown). The crankshaft 79 is journaled by a plurality of bearings within the engine body 72 to rotate about a crankshaft axis which is generally parallel with the longitudinal axis of the watercraft 20.

[0047] The cylinder head 76 is provided with individual recesses which cooperate with the respective cylinder bores 65 and heads of the pistons to form combustion chambers. Poppet-type intake valves are slideably supported in the cylinder head in a known manner, and have their head portions engageable with valve seats so as to control the flow of the intake charge into the combustion chambers through the intake passages 66. The intake valves are operated by an intake camshaft 80 which is journaled in the cylinder head 76. The cylinder head 76 also includes at least one exhaust passage for each of the combustion chambers. The exhaust passages emanate from one or more valve seats formed in the cylinder head, and cooperate with an exhaust system for discharging exhaust gasses to the atmosphere. At least one exhaust valve is supported for reciprocation in the cylinder head for each combustion chamber, in a manner similar to the intake valves. The exhaust valves are operated by an exhaust camshaft 82, which is journaled in the cylinder head 76.

[0048] With reference to FIG. 11, both the intake and exhaust camshafts 80, 82 are driven by the crankshaft 79. A drive member, such as a drive gear 84, is connected to one end of the crankshaft 79. A first driven member 86 is connected to the intake camshaft 80 and a second driven member 88 is connected to the exhaust camshaft 82. Thus, the drive member 84 drives the first and second driven members 86, 88 through a torque transmission member, such as a drive chain 90 or drive belt, as is well known in the art. The intake and exhaust camshafts 80, 82 and the intake and exhaust valves form a valve train of the engine 52.

[0049] A suitable ignition system is provided for igniting the air and fuel mixture provided to each combustion chamber. Sparkplugs (not shown) preferably are fired by the ignition system, which preferably includes an electronic control unit (ECU) (not shown) connected to the engine 52 by one or more electrical cables. A pulser-coil (not shown) which may be incorporated into the ECU, generates firing signals for the ignition system. In addition, the ignition system may include a battery for use in providing electric power to an electric starter and the like.

[0050] With reference to FIG. 3, the watercraft 20 also includes a lubrication system. The lubrication system desirably includes a lubricant reservoir 90, lubricant filter (not shown) and a lubricant pump (not shown). The lubricant pump is configured to circulate lubricant between the reservoir 90, the filter, and at least one lubricant gallery formed in the engine body 72. Preferably, the lubricant reservoir 90 is in the form of a tank mounted to the rear of the engine body 72. The lubricant reservoir 90 preferably includes a lubricant fill tube (not shown) which extends upwardly to a lubricant fill port. The lubricant fill port is arranged to be accessible through the access opening in the seat pedestal 44.

[0051] The lubricant reservoir 90 communicates with the lubricant pump through a lubricant supply and lubricant return lines (not shown). The lubricant pump can be in the form of a single pump or the pump mechanism can comprise a supply pump and return or a “scavenge” pump. The lubrication functions of the lubrication system in the illustrated embodiment can be of a conventional type, and thus, further description of the lubrication function of the lubrication system is not deemed necessary for one of ordinary skill in the art to make and use the invention as disclosed herein.

[0052] The engine 32 further includes an exhaust system 92 to discharge burnt charges (i.e., exhaust gases) from the combustion chambers. In the illustrated embodiment, the exhaust system 92 includes four exhaust ports (not shown). The exhaust ports are defined in the cylinder head member 76 and communicate with associated combustion chambers. As mentioned above, exhaust valves selectively connect and disconnect the exhaust ports with the combustion chambers. That is, the exhaust valves selectively open and close the exhaust ports.

[0053] As illustrated in FIGS. 1-3, the exhaust system includes an exhaust manifold 94. In a presently preferred embodiment, the manifold 94 comprises a first exhaust manifold 96 and a second exhaust manifold 98 coupled with the exhaust ports on the starboard side of the engine 52 to receive exhaust gases from the respective ports. The first exhaust manifold 96 is connected with two of the exhaust ports and the second exhaust manifold 98 is connected with the other two exhaust ports. In a presently preferred embodiment, with reference to FIG. 6, the first and second exhaust manifolds 96, 98 are configured to nest with each other.

[0054] Respective downstream ends of the first and second exhaust manifolds 96, 98 are coupled with a first unitary exhaust conduit 100. The first unitary conduit 100 is further coupled with a second unitary exhaust conduit 102. The second unitary conduit 102 is then coupled with an exhaust pipe 104 on the rear side of the engine body 72.

[0055] With reference to FIG. 8, the exhaust pipe 104 extends rearwardly along the port side of the engine body 72. The exhaust pipe 104 is then connected to a water-lock 106 (FIG. 9) at a forward surface of the water-lock 106. With reference to FIGS. 1 and 2, a discharge pipe 108 extends from a top surface of the water-lock 106 and transversely across the center plane CP. The discharge pipe 108 then extends rearwardly and opens at a stem of the lower hull section 24 in a submerged position. The water-lock 106 inhibits the water in the discharge pipe 108 from entering the exhaust pipe 104.

[0056] The first and second exhaust manifolds 96, 98 are affixed to the cylinder head member 76 on the starboard side, preferably by a plurality of bolts. With reference to FIG. 6, the first exhaust manifold 96 and the second exhaust manifold 98 have upstream ends 96 a, 98 a and downstream ends 96 b, 98 b, respectively. The first manifold 96 defines two exhaust passages 114 c 1, 114 c 4, and the second manifold 98 also defines two exhaust passages 116 c 2, 116 c 3. The exhaust passages 114 c 1, 114 c 4 of the first manifold 98 communicate with exhaust ports of the first and fourth cylinders, Respectively, at the upstream ends 96 a. The exhaust passages 116 c 2, 116 c 3 of the second manifold 98 communicate with exhaust ports of the second and third cylinders, respectively, at the upstream ends 98 a. The first and second manifolds 96, 98 bifurcate symmetrically. The downstream ends 96 b, 98 b converge so that the downstream ends 96 b, 98 b are directed downwardly. The downstream ends 98 b of the second manifold 98 are positioned between the downstream ends 96 b of the first manifold 96 and the engine body 72.

[0057] The cooling system of the engine 52 includes an exhaust cooling system, a lubricant cooling system, and an engine cooling system. The first and second manifolds 96, 98 define water jackets 118, 120 irrespectively as part of the exhaust cooling system around the exhaust passages 114 c 1, 114 c 4, 116 c 2, 116 c 3. In the illustrated embodiment, with reference to FIGS. 7 and 8, the cooling water used for the exhaust cooling system is introduced into the system through at least one water inlet port 122 disposed in the second unitary conduit 102. At least one external water conduit 123 (FIG. 3) preferably couples the inlet port 122 with the jet pump unit 61 downstream of the impeller 170 so as to deliver water that is pressurized by the rotation of the impeller, described in greater detail below. However, other suitable cooling water supply arrangements may also be used, such as a mechanical pump coupled to the crankshaft 79, for example.

[0058] As described above, in the illustrated embodiment, two exhaust manifolds 96, 98 are provided for four exhaust ports of the engine body 72. Both the first and second exhaust manifolds 96, 98 are coupled with the first unitary exhaust conduit 100 at the respective downstream ends 96 b, 98 b. The respective downstream ends 96 b, 98 b define flange portions 124, 126 and a plurality of bolt holes 128, 130 are provided there for the coupling.

[0059] With reference to FIG. 7, the first unitary conduit 100 has a curved configuration and is oriented such that one end, i.e., the upstream end 100 a is directed upwardly, and the other end, i.e., the downstream end 100 b, is directed forwardly and upwardly. That is, a curved portion is placed at the lowermost position and the downstream end 100 b is slanting upward. The first unitary conduit 100 extends generally along the starboard side of the engine body 72.

[0060] The first unitary conduit 100 has four exhaust passages (not shown), two of which are juxtaposed and communicate with the exhaust passages 114 c 1, 114 c 4 of the first manifold 96. The other two exhaust passages of the first unitary conduit 100, are juxtaposed and communicate with the exhaust passages 116 c 4, 116 c 3 of the second manifold 98. The set of exhaust passages in communication with the first manifold 96 is positioned outside of the set of exhaust passages communicating with the second manifold 98. The upstream end 100 a of the first unitary conduit 100 defines a flange portion 132 and a plurality of bolt holes (not shown) are provided there. The flange portion 132 abuts the flange portions 124, 126 of the first and second manifolds 96, 98 and is affixed thereto by bolts.

[0061] The first unitary exhaust conduit 100 is coupled with the second unitary exhaust conduit 102 at the downstream end 100 b. The downstream end 100 b defines a flange portion 134 and a plurality of bolt holes are provided there for the coupling.

[0062] The first unitary exhaust conduit 100 defines a water jacket (not shown) coupled with the water jackets 118, 120 of the first and second manifolds 96, 98. The water jacket is disposed around the four exhaust passages of the first unitary conduit 100.

[0063] As illustrated in FIGS. 7 and 8, the second unitary conduit 102 also has a curved configuration. The second unitary conduit 102 is oriented such that one end, i.e., the upstream end 102 a, is directed rearwardly and downwardly, and the other end, i.e., downstream end 102 b, is directed laterally. That is, the upstream end 102 a is slanting with an angle that is the same as the angle of the downstream end 100 b of the first unitary conduit 100. The second unitary conduit 102 thus extends contiguously from the first unitary conduit 100 and generally upwardly and forwardly.

[0064] The second unitary conduit 102 has four exhaust passages 102 c 1, 102 c 2, 102 c 3, 102 c 4 which communicate with the four exhaust passages of the first unitary exhaust conduit 100. Like the exhaust passages of the first unitary conduit 100, the exhaust passages 102 c 1, 102 c 2, 102 c 3, 102 c 4 are preferably disposed radially.

[0065] The second unitary conduit 102 has a water jacket 136 disposed in a space around the four exhaust passages 102 c 1, 102 c 2, 102 c 3, 102 c 4. As mentioned above, the water inlet port 122 disposed in the second unitary conduit 102 supplies cooling water from a high-pressure portion 175 of the jet pump unit 61 to the exhaust cooling system and, specifically, to the water jacket 136 of the second unitary conduit 102. Due to the water inlet port 122 being positioned at a relatively high vertical position on the first unitary conduit 100, and because the second unitary conduit 102 is vertically higher than the first unitary conduit 100, at least a portion of the cooling water flows from the inlet port 122 toward the first unitary conduit 100. In other words, in a direction opposite of exhaust gas flow, as indicated in phantom by the arrow 137.

[0066] The second unitary conduit 102 also includes a water outlet port 138 (FIG. 7) in fluidic communication with the water jacket 136. Desirably, the water outlet port 138 is connected to a tell-tale port (not shown) on the side of the hull 22 by one or more conduits (not shown), as is known in the art. The water outlet port 138 is advantageously positioned vertically higher than the water inlet port 122 to ensure that the water jacket 136 is entirely filled with cooling fluid before fluid exits from the tell-tale port. In this manner, the accuracy of the visual indication of the proper functioning of the exhaust cooling system (e.g., water being expelled through the tell-tale port) is desirably improved.

[0067] A flange portion 140 of the secondary exhaust conduit 102 desirably has four bolt holes. The flange portion 140 abuts on the flange portion 134 of the first unitary conduit 100 and is affixed thereto by four bolts 142.

[0068] With reference to FIG. 8, the second unitary exhaust conduit 102 is coupled with the exhaust pipe 104 at the downstream end 102 b. The downstream end 102 b defines an inner coupling portion 144 and an outer coupling portion 146. The outer coupling portion 146 has an outer diameter larger than a diameter of the inner coupling portion 144 and extends outward from the inner coupling portion 144.

[0069] With reference to FIG. 8, the exhaust pipe 104 also defines a water jacket 148 around an exhaust passage 150 so as to form a dual pipe structure. That is, the exhaust passage 150 is defined within an inner tube portion 152, while the water jacket 148 is defined between the inner tube portion 152 and an outer tube portion 154. The outer coupling portion 146 surrounds the outer tube portion 154 and the inner coupling portion 144 fits within the inner tube portion 152. A sleeve 156 surrounds the intersection of the inner coupling portion 144 and inner tube portion 152 to substantially create a seal therebetween. Additional fastening members are also preferably employed to couple the second unitary conduit 102 and the exhaust pipe 104, such as a rubber bellow (not shown) extending over the connection, for example. Preferably, a pair of band members (not shown) are further wound around the rubber bellow for fastening it tightly.

[0070] The single exhaust passage 150 of the exhaust pipe 104 communicates with the exhaust passages 102 c 1, 102 c 2, 102 c 3, 102 c 4 of the second unitary conduit 102. The cross sectional area of the exhaust passage 150 is preferably greater than the total cross sectional areas of the exhaust passages 102 c 1, 102 c 2, 102 c 3, 102 c 4. The water jacket 136 of the second unitary conduit 102 communicates with the water jacket 148 of the exhaust pipe 104. The cooling water thus flows continuously to the water jacket 148 from the water jacket 136 as indicated by the arrows 158 of FIG. 8.

[0071] The exhaust pipe 104 extends from the second unitary conduit 102 to the water-lock 106 along the port side of the engine body 72. Desirably, a downstream portion of the exhaust pipe 104 is coupled with a forward portion of the water-lock 106, as illustrated in detail in FIG. 9. An inlet tube 160 of the water-lock 106 is spaced apart from a downstream end 104 b of the exhaust pipe 104. A rubber hose 162 connects the exhaust pipe 104 and water-lock 106 and is fitted onto an outer surface of each of the downstream end 104 b and the inlet tube 160. A band (not shown) may be disposed around an upstream portion 162 a of the rubber hose 162 to fasten the portion 162 a to the downstream end 104 b of the exhaust pipe 104. Another band (not shown) may be disposed around a downstream portion 162 b of the rubber hose 162 to fasten the portion 162 b to the inlet tube 160 of the water-lock 106.

[0072] Because no specific water jacket is defined in both the rubber hose 162 and the inlet tube 160, the water coming from the water jacket 148 of the exhaust pipe 104 merges with exhaust gases discharged from the exhaust passage 150. The water then moves downstream and enters the water-lock 106 together with the exhaust gases.

[0073] Preferably, the transition between the exhaust pipe 106 and rubber hose 162 includes features which inhibit cooling water from entering the exhaust passage 150 of the exhaust pipe 106. Specifically, an exhaust pipe extension tube 164 is connected to the downstream end 104 b of the exhaust pipe 104, preferably by a plurality of fasteners, such as bolts 166 (one shown). The extension tube defines transition zones 148 b, 150 b of the water jacket 148 and exhaust passage 150, respectively. This feature inhibits cooling water from splashing into the exhaust passage 150 as it moves from the water jacket 148 to the larger cross-sectional area of the rubber hose 162.

[0074] Additionally, an internal surface of the downstream end 104 b of the exhaust pipe 104 defines a inwardly extending annular projection, or stopper rib 166. The stopper rib 166 extends substantially radially with respect to the inner tube portion 152 of the exhaust pipe 104 and is spaced upstream from the opening at the downstream end 104 b. The stopper rib 166 operates to inhibit any water that may splash onto the inner surfaces of the extension tube 164 or downstream end 104 b from moving along those surfaces and into the exhaust passage 150.

[0075] In operation, the exhaust gases of the respective combustion chambers move to the associated exhaust ports and then go to the first or second exhaust manifolds 96, 98 which are associated with the respective exhaust ports. The exhaust gases then pass through the associated exhaust passages of the first and second unitary exhaust conduits 100, 102. The exhaust gases coming from the respective cylinders are separated from each other until they reach the downstream end 102 b of the second unitary conduit 102. The exhaust gases merge together when moving into the exhaust pipe 104 from the second unitary conduit 102. The exhaust gases flow through the exhaust pipe 104 and then enter the water-lock 106. The exhaust gases move to the discharge pipe 108 from the water-lock 106 and are finally discharged to the body of water at the stern of the lower hull section 24 in a submerged position. The water-lock 106 primarily inhibits the water in the discharge pipe 108 from entering the exhaust pipe 104. Because the water-lock 106 has a relatively large volume, it may function as an expansion chamber also.

[0076] With reference to FIG. 10, a preferred embodiment of the present cooling system is illustrated schematically. In operation, water from the body of water in which the watercraft 20 is operating is drawn into the impeller housing 63 by the impeller 170. In the present embodiment, the cooling system supplies coolant, which is water from the body of the water in which the watercraft 10 operates, independently to the exhaust system, the lubrication system and the engine body 72.

[0077] In the presently preferred embodiment, a primary coolant supply passage 172 extends from a positive pressure portion 175 of the impeller housing 63 to supply cooling fluid, or coolant, to various systems of the watercraft 20, such as the exhaust system, lubrication system and the engine body 72, described in detail below. However, it is conceived that a plurality of coolant passages (not shown) can extend from the impeller housing 63 to independently provide coolant to the desired systems.

[0078] The primary coolant supply passage 172 extends from the impeller housing 63 to a splitter, or Y-connection 176. A connection passage 177 extends from one branch of the Y-connection 176 to a second Y-connection 180. An engine supply coolant passage 182 extends from the other branch of the Y-connection 176 to the engine cooling system, as described below.

[0079] An exhaust coolant passage 178 extends from one branch of the second Y-connection 180 to supply the exhaust cooling system with coolant. Specifically, with additional reference to FIG. 7, the coolant passage 178 is connected to the water inlet 122 on the second unitary exhaust conduit 102. Thus, the coolant passage 178 supplies the cooling jacket 136 with water from the impeller housing 63, where it moves through the exhaust cooling system as described above with reference to FIGS. 5-9.

[0080] As shown schematically in FIG. 10, a coolant passage, or drain tube 184, connects the water outlet port 138 of the second unitary exhaust conduit 102, described above with reference to FIG. 7, to a discharge 186. Preferably, the discharge 186 is in the form of a tell-tale port positioned on the hull 22 so as to produce a visible stream of discharged coolant which signals the operator of the watercraft 20 that the cooling system appears to be operational.

[0081] Downstream from the second unitary conduit 102, the end of the coolant passage 148 of the exhaust pipe 104 is schematically represented by discharge 188. A coolant passage 190 connects the discharge 188 to a downstream discharge 190, which represents the end opening of the discharge pipe 108. In FIG. 10, the water lock 106 has been omitted for the purpose of clarity, although, if shown, the water lock 106 would be located along the coolant passage 190 intermediate discharges 188 and 192.

[0082] Returning to the second Y-connection 180, a lubricant coolant supply passage 194 extends from a second branch of the Y-connection 180 to the lubricant reservoir 90. Coolant is delivered through the supply passage 194 to a water jacket (not shown) of the reservoir 90. Coolant exits the reservoir 90 through a coolant, or discharge passage 196 to a junction 198. The junction 198 may comprise a Y-connection or T-connection, or other suitable arrangement to converge two or more passages into a single passage. From the junction 198, a coolant drain passage 200 extends to a discharge 202, which expels the coolant to the atmosphere. The drain passage 200 and discharge 202 may be separate from, or may be wholly or partially coextensive with the coolant passage 190 and discharge 192, described immediately above.

[0083] As mentioned above, the engine coolant supply passage 182 extends from Y-connector 176 to deliver coolant to the engine body 72. Specifically, the supply passage 182 is coupled at its downstream end to a pressure actuated valve 210 (illustrated schematically in FIG. 10) which, in turn, is coupled to the engine body 72. The pressure actuated valve 210 permits coolant to flow into the engine body 72. Further, if the supply coolant pressure, and more specifically, the coolant pressure within the valve 210 itself, exceeds a predetermined threshold, the valve 210 permits coolant to flow to the coolant bypass passage 212 and thereby bypass the engine body 72. In the illustrated embodiment, the coolant bypass passage 212 extends from the pressure actuated valve 210 to a water jacket of the lubricant reservoir 90. Within the water jacket of the reservoir 90, coolant from passage 212 combines with coolant from supply passage 194 and is similarly expelled through discharge passage 196.

[0084] With reference to FIGS. 11-13, the structure of a preferred pressure actuated valve 210 is shown in greater detail. The valve 210 comprises a valve body 220 having an inlet 222 and first and second outlets 224, 226. The inlet 222 is connected to the engine coolant supply passage 182. The first outlet 224 is connected to a water jacket 228 of the engine body 72 (FIG. 13). As is conventional, the water jacket 228 desirably surrounds a substantial portion of the cylinder bore 65. The water jacket 228 also preferably communicates with water jackets surrounding the remaining cylinder bores as well as water jackets of the cylinder head 76, which desirably substantially surround the combustion chambers. The second outlet 226 is connected to the coolant bypass passage 212.

[0085] Desirably, the inlet 222 and second outlet 226 comprise conventional hose fittings and the passages 182, 212 are defined by suitable coolant hoses, such as reinforced rubber hoses for example. In addition, conventional hose clamps are desirably employed to provide a secure connection. With reference to FIG. 13, the illustrated inlet 222 is formed separately from the valve body 220 and coupled thereto by a suitable arrangement, such as a press fit arrangement with or without adhesives, mechanical fasteners or the like. As illustrated, the second outlet 226 is unitarily formed with the valve body 220. Although this is a preferred arrangement, other suitable arrangements may also be used.

[0086] With continued reference to FIG. 13, the first outlet 224 comprises an internal sleeve 230 coupled to the valve body 220. A protruding portion of the internal sleeve 230 is held within a port 232 defined by the cylinder block 74 of the engine body 72. The internal sleeve 230 may be press fit into both the valve body 220 and cylinder block 74. In addition, a suitable adhesive may be used to prevent loosening of the valve 210. Other suitable arrangements may also be used to couple the valve 210 to the engine body 72.

[0087] With additional reference to FIGS. 11 and 12, as mentioned above, the pressure actuated valve is coupled to the cylinder block 74 of the engine 52 and, preferably, to the starboard side of the cylinder block 74. Preferred placement of the valve 210 is additionally illustrated in phantom in FIGS. 3 and 4.

[0088] The valve body 220 is desirably comprised of an upper valve portion 234 and a lower valve portion 236. In the illustrated embodiment, the upper and lower valve portions 234, 236 are coupled by a pair of fasteners, such as bolts 238, however, other suitable methods of coupling may also be used. Preferably, the inlet 222 and first outlet 224 extend from the upper valve portion 234 and the second outlet extends from the lower valve portion 236.

[0089] The valve body 220 defines an internal chamber which is divided into upper and lower chamber portions 239, 240, respectively, by a moveable piston 242. The inlet 222 and first outlet 224 are in direct communication with the upper chamber portion 239 and the second inlet 226 is in direct communication with the lower chamber portion 240. Thus, the moveable piston 242 functions as a valve to selectively permit fluid communication between the upper and lower chamber portions 239, 240 and, thus, permit coolant to flow from the supply passage 182 to the bypass passage 212.

[0090] The piston 242 is supported for axial movement by a grommet 244 which is, in turn fixedly supported by a flange member 246 positioned between the upper and lower valve portions 234, 236. The piston 242 is biased into a closed position by a biasing member, such as spring 248. The piston 242 is opened in response to fluid pressure in the upper chamber portion 238 exceeding a predetermined threshold, which is determined at least in part by the spring constant of the spring 248 and the surface area of the piston 242 transverse to its axis of motion, as may be determined by one of skill in the art.

[0091] When the coolant pressure within the upper chamber portion 239 exceeds the predetermined threshold, the piston moves downwardly against the biasing force of the spring 248 and permits coolant to flow from the upper chamber portion 239 to the lower chamber portion 240. A variety of suitable arrangements may be provided to permit such flow. For example, the piston 242 and grommet 246 may cooperate in a tapered fit arrangement or axial movement of the piston 242 may uncover passages within the piston 242 that are normally covered by the grommet 246 in the closed position. Other suitable arrangements may also be employed.

[0092] With reference to FIG. 10, an engine coolant return passage 250 connects the water jacket 228 of the engine body 72 with a temperature actuated valve, or thermostat 252. As is conventional, the thermostat 252 prohibits coolant below a predetermined threshold temperature from passing through the thermostat 252 and permits coolant at or above a predetermined threshold temperature to pass through the thermostat 252. From the thermostat 252, coolant flows through coolant passage 254 to junction 198. As described above, coolant flows from the junction 198 through discharge passage 200 and is expelled to the atmosphere through discharge 202.

[0093] With reference to FIG. 14, the structure of a preferred thermostat 252 is illustrated in greater detail. The thermostat 252 includes a body, or housing 256 which defines an internal passage 258. As described above, the engine coolant return passage 250 is connected to an upstream side of the thermostat 252 and the coolant passage 254 is connected to a downstream side of the thermostat 252.

[0094] A nozzle member 260 is supported axially within the internal passage 258 and defines an opening 262. The nozzle 260 is arranged within the internal passage 258 such that fluid is prevented from passing the nozzle 260 except through the opening 262. A temperature sensitive element 264 is supported within the opening 262 by a biasing element, such as spring 266. As is conventional, when the temperature sensitive element 264 is below a predetermined threshold temperature, it occupies substantially the entire opening 262 and substantially prevents fluid flow through the thermostat 252. When the temperature sensitive element 264 is at or above a predetermined threshold temperature, it permits fluid flow through the opening 262. However, other suitable temperature sensitive valve arrangements may also be used.

[0095] As realized by the present inventors, conventional temperature actuated valves, such as the thermostat 252, can undesirably permit fluid to pass through the valve when the fluid pressure on an upstream side of the valve is above a certain threshold pressure even when the temperature is not above the predetermined temperature threshold. This situation may occur because the temperature sensitive valve may not be capable of retaining fluid above a certain pressure (referred to herein as the “blowby” pressure) due to the fit necessary between components of the valve to ensure proper operation, or due to normal manufacturing tolerance variations. Repeated blowby of fluid through the temperature sensitive valve when it is in its closed orientation may affect the accuracy of the valve, or may render it entirely inoperable. As a result, the engine may not be maintained at a desired operating temperature.

[0096] The presently preferred cooling system overcomes this problem and substantially reduces, or eliminates, possible damage to the thermostat 252 due to excessive upstream pressure above a blowby pressure, which could result in coolant flow through the thermostat 252 when the thermostat is in a closed orientation. For example, in a preferred operation of the cooling system, upon initial startup of the engine 52 or when the engine 52 is otherwise operating at a relatively low temperature, the thermostat 252 remains closed. Coolant supplied to the engine 52 from the positive pressure portion of the jet pump unit 175 is prevented from exiting the water jacket 228 of the engine body 72 by the thermostat 252. Accordingly, the engine temperature is permitted to rise to a predetermined threshold operating temperature, such as about 50° Celsius for example. Ensuring that the engine 52 operates at a desired temperature, or within a desired temperature range, accommodates more complete combustion and, therefore, results in a lower amount of noxious emissions.

[0097] Coolant supplied to the exhaust cooling system and lubrication cooling system, however, is permitted to flow in accordance with the flow paths described above in detail. Temperature dependent control of the exhaust and lubrication cooling systems is not deemed necessary because the proper operation of the exhaust and lubrication systems is less critical to the performance of the engine 52. However, if desired, the cooling systems of the exhaust system and lubrication system may incorporate temperature actuated valves.

[0098] If the coolant temperature within the thermostat 252 remains below the predetermined threshold temperature, but the coolant supply pressure at the pressure actuated valve 210 is above the predetermined threshold pressure, the pressure actuated valve 210 opens to permit a portion of coolant to flow into the bypass passage 212, thereby bypassing the engine 52 and the thermostat 252. Because the coolant temperature within the thermostat 252 is below the predetermined opening threshold temperature, the thermostat 252 remains closed and retains coolant within the engine 52 to allow the engine 52 to achieve a desired operating temperature.

[0099] Preferably, the threshold pressure for the pressure actuated valve to open is desirably below the “blowby” pressure that may cause damage to the thermostat 252. Advantageously, with such an arrangement, the pressure actuated valve 210 maintains the supply coolant pressure at or below the threshold opening pressure of the valve 210. Thus, the coolant pressure within the thermostat 252 is prevented from reaching a magnitude that can cause damage. Therefore, the preferred cooling system alleviates such a potential failure of the thermostat 252.

[0100] Once the temperature of the coolant within the thermostat 252 reaches the threshold opening temperature, the thermostat 252 opens to permit fluid flow therethrough and maintain the operating temperature of the engine 52 at approximately the desired level. When the thermostat 252 is in an open orientation, the pressure actuated valve 210 will nonetheless open when the fluid pressure reaches the predetermined opening pressure of the valve 210 thereby maintaining a desirable maximum pressure level within the cooling system.

[0101] Of course, the foregoing description is that of certain features, aspects and advantages of the present invention to which various changes and modifications may be made without departing from the spirit and scope of the present invention. Moreover, a watercraft may not feature all objects and advantages discussed above to use certain features, aspects and advantages of the present invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. The present invention, therefore, should only be defined by the appended claims. 

What is claimed is:
 1. A small watercraft comprising a hull defining an engine compartment, an internal combustion engine disposed in the engine compartment, a propulsion device driven by the engine, the engine having an engine body defining a combustion chamber, a cooling jacket at least partially surrounding the combustion chamber, a cooling system in fluid communication with the cooling jacket, the cooling system supplying cooling fluid to the cooling jacket and comprising a pressure actuated valve and a temperature actuated valve, the cooling jacket being between the pressure actuated valve and the temperature actuated valve.
 2. The small watercraft of claim 1, wherein the pressure-activated valve permits cooling fluid to bypass the engine when the cooling fluid upstream from the temperature actuated valve is above a predetermined threshold pressure.
 3. The small watercraft of claim 1, wherein the temperature actuated valve substantially prevents cooling fluid to from exiting the engine body when the cooling fluid within the cooling jacket is below a predetermined temperature.
 4. The small watercraft of claim 3, wherein the predetermined temperature is about 50 degrees centigrade.
 5. The small watercraft of claim 1, additionally comprising a lubrication system including a lubricant reservoir, the cooling system comprising a reservoir supply passage for supplying cooling fluid to a cooling jacket of the reservoir independently of the engine.
 6. The small watercraft of claim 1, additionally comprising an exhaust system, the cooling system including an exhaust supply passage for supplying cooling fluid to a cooling jacket of the exhaust system.
 7. A method of cooling a watercraft engine having an engine body comprising providing a cooling system to deliver a supply of cooling fluid to a water jacket of the engine body, detecting a temperature of the cooling fluid downstream from the water jacket with a thermostat and substantially preventing cooling water from evacuating the water jacket if the temperature is below a predetermined threshold, detecting a pressure of the cooling fluid upstream from the thermostat and allowing at least a portion of the cooling fluid to bypass the thermostat if the pressure is above a predetermined threshold, the predetermined threshold being a pressure lower than a blow-by pressure of the temperature actuated valve.
 8. The method of claim 7, wherein the detection of the cooling fluid pressure takes place upstream from the water jacket and the cooling water additionally bypasses the water jacket if the pressure is above the predetermined threshold.
 9. The method of claim 7, additionally comprising providing a supply of fluid to one of an exhaust cooling system and a lubrication cooling system independently from the supply of cooling fluid to the engine body.
 10. A marine engine comprising an engine body defining at least one combustion chamber, a cooling jacket at least partially surrounding the at least one combustion chamber, a cooling system in fluid communication with the cooling jacket, the cooling system supplying cooling fluid to the cooling jacket and comprising a pressure actuated valve and a temperature actuated valve, the pressure actuated valve being upstream from the temperature actuated valve and configured to permit the cooling fluid to bypass the temperature actuated valve if a pressure of the cooling fluid is above a predetermined threshold, the predetermined threshold being a pressure lower than a blow-by pressure of the temperature actuated valve.
 11. The marine engine of claim 10, wherein the cooling jacket is positioned between the pressure actuated valve and the temperature actuated valve and the pressure actuated valve is configured to permit the cooling fluid to additionally bypass the cooling jacket.
 12. The small watercraft of claim 10, wherein the temperature actuated valve substantially prevents cooling fluid to from exiting the engine body when the cooling fluid within the cooling jacket is below a predetermined temperature.
 13. The small watercraft of claim 12, wherein the predetermined temperature is about 50 degrees centigrade.
 14. The small watercraft of claim 10, additionally comprising a lubrication system including a lubricant reservoir, the cooling system comprising a reservoir supply passage for supplying cooling fluid to a cooling jacket of the reservoir independently of the engine.
 15. The small watercraft of claim 10, additionally comprising an exhaust system, the cooling system including an exhaust supply passage for supplying cooling fluid to a cooling jacket of the exhaust system. 